Humans are unreasonable creatures bound by insufferable emotion and grudges. Still worthwhile to talk to them and maybe find out why they're suffering.

[gets misty-eyed at the mention of tea and biscuits, but powers through. starts rooting around in his pockets for his cigarettes.]

Most important thing to remember with demons is that exorcism usually isn't death. Unless you're unpossessable for some reason, make certain either you're in a protective circle, to keep the demon out, or it is, to keep it in.